Film forming apparatus and film forming method

ABSTRACT

A film forming apparatus comprising a substrate holding section for holding a substrate to be processed, a nozzle unit arranged and opposing the substrate holding section, having a discharge hole for continuously applying film-forming solution, in the form of a slender stream, to a surface of a substrate held by the substrate holding section, and a drive mechanism for driving the substrate and the nozzle unit relative to each other, thereby to coat the surface of the substrate with the solution, while the nozzle unit is applying the solution, in the form of a slender stream, to the surface of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional under 37 C.F.R. 1.53 (b) ofpending U.S. patent application Ser. No. 09/328,771, filed Jun. 9, 1999,which is based upon and claims benefit of priority of Japanese PatentApplication No. 10-173229, filed Jun. 19, 1998, and Japanese PatentApplication No. 10-364943, filed Dec. 22, 1998, whereby the entirecontents of the three patent applications are being incorporated hereinby reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a film forming apparatus whichapplies a solution having resin or the like dissolved in it,particularly a resist solution, onto a substrate to be processed, suchas a semiconductor wafer, an LC substrate, an exposure mask, or thelike.

[0003] In the process of manufacturing an LCD or a semiconductor device,for example, photolithography technique is employed to form minutecircuit patterns.

[0004] In the photolithography technique, resist solution is applied tothe surface of a substrate to be processed, such as an LCD substrate, asemiconductor wafer, or the like, thereby forming a film thereon.Thereafter, the film is light-exposed to a specific pattern. Further,the film is subjected to developing and etching, to have a specificcircuit pattern.

[0005] At present, the spin coating method is most popular as a methodof applying resist solution to a substrate to be process and forming afilm thereon. In the spin coating method, the resist solution is drippedonto the center part of the substrate, and the substrate is rotated athigh speed. The resist solution is thereby spread over the entiresurface of the substrate by virtue of centrifugal force. As a result, aresist solution film, which is substantially uniform, can be is formedall over the surface of the substrate.

[0006] In recent years, there is the trend that circuit patterns to beformed by photolithography technique have smaller and small wire width.It is therefore strongly demanded that the resist film be made thin.Namely, since the wire width of the circuit to be formed is proportionalto the thickness of the resist film and the wavelength of exposurelight, it is desirable to make the resist film as thin as is possible.

[0007] With the spin coating method it is possible to reduce thethickness of the resist film, by increasing the rotation speed of thesubstrate. Thus, an 8-inch wafer, for example, is rotated at aconsiderably high speed of 2000 to 4000 rpm.

[0008] The resist applying method, which uses the conventional spincoating method, has the following problems that should be solved.

[0009] (1) In the spin coating method, if the substrate to be processedis large, its the circumferential speed is high, causing a turbulentflow of air. The turbulent flow may vary the thickness of the resistfilm. Due to this, the exposure resolution will be decreased.

[0010] The decrease in exposure resolution is a fatal obstruction to anintended increase in the integration density of semiconductor devices.Inevitably, with the conventional spin coating method it is difficult toobtain a uniform resist film having a thickness of 0.4 μm or less.Hence, there is limitation to the manufacture of semiconductor devicesof about several gigabytes.

[0011] (2) In the spin coating method, the solvent contained in theresist solution gradually evaporates as the resist solution spreads fromthe center part of the substrate toward the peripheral part thereof.Therefore, the viscosity of the resist solution changes in the directionthe solution spreads. Those parts of the resist film, which lie on thecenter and peripheral parts, respectively, may differ in terms ofthickness.

[0012] (3) In the spin coating method, the resist solution is wasted ina large amount, spinning off from the peripheral part of the wafer,because the substrate to be processed is rotated at high speed. In oneinstance, only 10% or less of the resist solution applied onto the wafercontributes to the forming of a resist film.

[0013] (4) Further, in the spin coating method, the wafer must berotated in a cup in order to receive the resist solution spinning off.The resist solution sticking to the cup form particles, which maycontaminate the substrate being processed. Hence, it is necessary towash the cup frequently.

[0014] (5) Still further, the spin coating method is disadvantageous inthat the resist solution may be applied also to that region of thesubstrate, such as the peripheral part, which does not contribute to theforming of a circuit. The resist solution applied to this part isusually removed right after the step of applying the resist solution, bya dedicated apparatus called “edge remover”.

BRIEF SUMMARY OF THE INVENTION

[0015] The present invention has been made in view of the factsmentioned in the paragraphs (1) to (5). Its principal object is toprovide a film forming apparatus which can greatly save the solutionused to form a film and which can uniformly apply the solution to onlythe desired part of the substrate that is to processed.

[0016] According to the first aspect of this invention, there isprovided a film forming apparatus which comprises: a substrate holdingsection for holding a substrate to be processed; a nozzle unit arrangedand opposing the substrate holding section, having a discharge hole forcontinuously applying film-forming solution, in the form of a slenderstream, to a surface of a substrate held by the substrate holdingsection; and a drive mechanism for driving the substrate and the nozzleunit relative to each other, thereby to coat the surface of thesubstrate with the solution, while the nozzle unit is applying thesolution, in the form of a slender stream, to the surface of thesubstrate.

[0017] With this structure it is possible to apply solution, such asresist solution, in a manner of so-called single-stroke writing.Therefore, the use efficiency of resist solution for forming a film canbe much increased. To form a thin film having a uniform thickness, it isnecessary to discharge the solution at high pressure in as slender astream as possible, while moving the nozzle unit at high speed. In thiscase, it is required that interruption of the solution stream beprevented effectively. To this end, it is desirable to provide anatmosphere control mechanism for maintaining a solvent atmosphere havinga predetermined concentration in a space into which the nozzle unitapplies the solution.

[0018] Here, the atmosphere control mechanism has a main body foraccommodating the substrate to be process, a solvent channel provided inthe main body for storing solvent controlled in temperature and surfacelevel, and a top plate member provided above the main body andpartitioning the space into which the nozzle unit applies the solution.In this case, the top plate member has an insertion section in which thenozzle unit is inserted.

[0019] Further, the top plate member may have heating means for heatingthe nozzle unit and the space into which the nozzle unit applies thesolution. If so, the solvent atmosphere can be controlled better, andthe viscosity of the solution can be controlled as is desired.

[0020] Preferably, the nozzle unit has a solution nozzle for applyingthe solution in the form of a slender stream, and a solvent nozzle forpassing solvent around the solution applied from the solution nozzle.

[0021] In this case, the solvent is prevented from evaporating from thesolution immediately after the solution is discharged from the nozzleunit, thus effectively the viscosity of the solution from changing.Interruption of the slender stream of the solution can thereby beavoided.

[0022] A route-speed setting section may be provided to set a speed atwhich the nozzle unit and the substrate are moved relative to each otherand a route along which the solution is to be applied, in accordancewith the amount of solution to apply, the time of applying the solutionand the area to coat with the solution. Then, a film of the solution,which is thin and has a uniform thickness, can be formed on thesubstrate.

[0023] Various types of solution application routes can be set. Forexample, a zigzag route or a spiral route may be set.

[0024] To render the thickness of the solution film uniform, it isnecessary to maintain the relative speed between the substrate and thenozzle at a constant value. To this end it is desired that a mask memberbe provided to cover the substrate, except a film-forming regionthereof, and that the nozzle unit and the substrate be decelerated,returned and accelerated over the mask member and moved at a constantrelative speed over the film-forming region of the substrate.

[0025] The mask member may be a plate having an opening that correspondsto the film-forming region. Alternatively, the mask member has a pair ofsolution receiving members and a drive mechanism for driving thesolution-receiving members to control a distance between the solutionreceiving members.

[0026] Further, the solution may be one selected from the groupconsisting of resist solution, solution for forming an interlayerinsulating film, solution for forming a highly conductive film,ferroelectric solution, sliver paste and the like.

[0027] According to the second aspect of the present invention, there isprovided an apparatus for forming a film on a substrate to be processed,which comprises: a substrate holding section for holding the substrate,with the surface thereof turned downwards; a nozzle unit having adischarge hole for discharging the solution in a form of a slenderstream, the discharging hole turned upwards and opposing the substrateheld by the substrate holding section; and a drive mechanism for drivingthe substrate holding section and the nozzle unit relative to eachother, thereby to coat the surface of the substrate with the solution,while the nozzle unit is applying the solution, in the form of a slenderstream, to the surface of the substrate.

[0028] With this structure it is possible to apply solution, such asresist solution, in a manner of so-called single-stroke writing. The useefficiency of resist solution for forming a film can therefore be muchincreased. Since the substrate is held with that surface turneddownwards and the solution is discharged upwards to coat the surface ofthe substrate, the substrate serves as a cover, effectively preventingsolvent from evaporating form the solution, such as resist solution. Asa result, Interruption of the slender stream of the solution can beavoided.

[0029] Moreover, with this structure, air can be easily expelled sincethe nozzle unit is arranged with its discharge hole turned upwards.

[0030] In the present invention, to form a thin film having a uniformthickness, the solution is discharged at high pressure in as slender astream as possible, while moving the nozzle unit at high speed. Thus, itis preferred that the discharge hole of the nozzle unit have a diameterof 10 to 200 μm.

[0031] It is desirable for this apparatus to further have a reversingmechanism for turning the substrate upside down. The reversing mechanismneeds to hold the substrate, without touching that surface of thesubstrate on which a film will be formed.

[0032] Such a slender nozzle as the one used in the present inventionhas the problem that the discharge hole is easily clogged when it stopsdischarging resist solution. It is therefore desirable that the nozzleunit have a solvent supplying mechanism for discharge a solvent throughthe discharge hole of the nozzle unit.

[0033] According to the third aspect of the present invention, there isprovided a method of forming a film on a surface of a substrate,comprising the steps of: holding a substrate to be processed; anddriving the substrate and a nozzle unit relative to each other, whilecontinuously applying film-forming solution, in the form of a slenderstream, to the surface of a substrate, thereby to form a film on thesubstrate.

[0034] With this method it is possible to apply solution, such as resistsolution, in a manner of so-called single-stroke writing. The useefficiency of resist solution for forming a film can therefore be muchincreased.

[0035] It is desirable that this method have a step of covering thesubstrate, except the film-forming region, with a mask member.

[0036] Preferably, the method further comprises an agitation step ofvibrating the substrate coated with the solution, thereby to render flata surface of a solution film formed on the substrate.

[0037] The method may comprise a step of holding the substrate, with thesurface, on which a film is to be formed, turned downwards, and thesubstrate and a nozzle unit may be driven relative to each other, whilecontinuously applying film-forming solution, in the form of a slenderstream, to a surface of a substrate, thereby to form a film on thesubstrate. In this case, the method needs to include a step of turningthe substrate upside down to hold the substrate with that surface turneddownwards.

[0038] It is desired that the method include a step of holding thenozzle unit at a wait position, before a film is formed on thesubstrate, and that solvent be passed through the discharge hole of thenozzle unit, thereby to prevent clogging in the discharge hole.

[0039] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate preferred embodimentsof the invention, and together with the general description given aboveand the detailed description of the preferred embodiments given below,serve to explain the principles of the invention.

[0041]FIG. 1 is a vertical sectional view schematically showing a resistsolution applying apparatus according to this invention;

[0042]FIG. 2 is a plan view of the resist solution applying apparatus;

[0043]FIG. 3 is a perspective view for explaining the route along whichthe resist solution is applied;

[0044]FIG. 4 is a vertical view depicting the main part of a nozzleunit;

[0045]FIG. 5 is a plane view of the coating/developing systemincorporating the resist solution applying apparatus according to thisinvention;

[0046]FIG. 6 is a side view of the coating/developing system;

[0047]FIG. 7 is a front view of the coating/developing system, forexplaining the function thereof;

[0048]FIG. 8 is a vertical sectional view showing another type of anozzle for use in the resist applying apparatus according to theinvention;

[0049]FIG. 9 is a perspective view illustrating another route alongwhich the resist solution is applied;

[0050]FIG. 10 is a plan view depicting still another route along whichthe resist solution is applied;

[0051]FIGS. 11A to 11D are perspective views of different mask members;

[0052]FIG. 12 is a perspective view for explaining the outline of themethod of forming a film by means of the resist solution applyingapparatus according to one embodiment of the invention;

[0053]FIGS. 13A and 13B are partial sectional views showing the resistapplying apparatus;

[0054]FIG. 14 is a plan view illustrating the resist applying apparatus;

[0055]FIG. 15 is a schematic diagram showing a nozzle unit and a systemconfiguration;

[0056]FIG. 16 is a perspective view showing a reversing mechanism; and

[0057]FIG. 17 is a flow chart for explaining the process of forming afilm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] Embodiments of the present invention will be described below,with reference to the accompanying drawings.

[0059] (First Embodiment)

[0060] First, the first embodiment of the invention will be describedwith reference to FIGS. 1 to 10 and FIGS. 11A to 11D.

[0061] The film forming apparatus according to this embodiment is, forexample, a resist solution applying apparatus that applies resistsolution (film-forming solution) to a semiconductor wafer (substrate tobe processed).

[0062] The present invention is characterized in that the resistsolution 3 is applied to only the circuit-forming region la of thewafer, in a manner of single-stroke writing, by moving a resist-solutionapplying nozzle unit 2 and the wafer 1 relative to each other as shownin FIG. 3. Namely, the resist solution is not applied to the wafer 1while the wafer 1 is being rotated at high speed as in the conventionalspin coating method.

[0063] In this embodiment, a mask member 4 is placed right above thewafer 1, covering the peripheral part of the wafer 1 and not coveringthe circuit-forming region la. The nozzle unit 2 is reciprocated in Xdirection, while intermittently moved in Y direction at a predeterminedpitch. The resist solution is thereby applied to the circuit-formingregion 1 a only.

[0064] In this invention, various measures, which will be explainedbelow, are taken to apply resist solution in a single-stroke writingmanner in the resist solution applying apparatus applied to thephotolithography technique employed in the manufacture of asemiconductor device.

[0065] (Resist Solution Applying Apparatus)

[0066]FIG. 1 is a vertical sectional view schematically showing thisresist solution applying apparatus, and FIG. 2 is a plan view of theapparatus.

[0067] As shown in FIG. 1, the apparatus has a frame 5, a wafer holder 6(substrate holding section of the invention) for holding thesemiconductor wafer 1, a temperature-controlled top plate 7 secured tothe frame 5 and covering the wafer holder 6, and the solution applyingnozzle unit 2 extending through a slit 7 a (insertion passage of theinvention) made in the top plate 7, opposing the wafer W1 and driven inX direction with respect to the wafer 1.

[0068] The frame 5 is, for example, a channel-shaped member opening atthe top, as is illustrated in FIG. 1. As shown in FIG. 2, the frame 5 iselongate, extending in the Y direction. Its one end, as viewed in the Ydirection, is a resist solution applying section R, and its other end isa wafer load/unload section L. A pair of Y rails 9 extend between theresist solution applying section R and the wafer load/unload section L,for holding the wafer holder 6 and allowing the same to move in the Ydirection.

[0069] Designated at numeral 10 in FIG. 2 is a ball screw mechanism fordriving the wafer holder 6 in the Y direction to position the same withrespect to the Y direction. The ball screw mechanism 10 has a ball screw11 rotatably supported by the walls 5 a and 5 b of the frame 5, whichare spaced in the Y direction, and a Y drive motor 12 for rotating theball screw 11.

[0070] As shown in FIG. 1, the wafer holder 6 is held on the Y rails 9,by way of a slider 13, to move in the Y direction. A nut 14 is securedto the lower surface of the wafer holder 6. The ball screw 11 is set inscrew engagement with the nut 14. Thus, the wafer holder 6 can be freelypositioned in the Y direction when the Y drive motor 12 rotates the ballscrew 11, which is set in screw engagement with the nut 14.

[0071] The wafer holder 6 has a cup-shaped main body 16 and a wafersuction table 17 for holding the wafer 1. The main body 16 has asolution channel 18, which opposes the lower surface of the wafer 1 inorder to store solvent (thinner solution). The solution channel 18 isfilled with the solvent, which is controlled in temperature and surfacelevel. The solvent evaporates, maintaining the wafer 1 in a solventatmosphere that has a predetermined concentration.

[0072] A solvent temperature control section 20 and a solvent supplyingsection 21 are connected to the solvent channel 18, to supply thesolvent and control the temperature and surface level of the solvent.The solvent temperature control section 20 may be one that suppliestemperature-controlled solvent into the solution channel 18.Alternatively, the section 20 may be one that controls a heater (heatingmeans of the invention) provided in the main body 16 to directly controlthe temperature of the solvent filled in the solvent channel 18.

[0073] The solvent supplying section 21 has means for monitoring thesurface level of the solvent in the solvent channel 18, such as apressure tube. Thus, the section 21 has the function of supplying thesolvent, while monitoring the surface level of the solvent. The solventmay be supplied in either replenishment scheme or circulation scheme. Inthe replenishment scheme, the solvent is replenished for only the amountevaporated from the solvent channel 18. In the circulation scheme, thesolvent is circulated in the loop passage on which the channel 18 andthe solvent supplying section 21 are provided.

[0074] In the corners of the bottom of the main body 16, which surroundthe wafer suction table 17 (wafer 1), four exhaust ports 19 a to 19 dare made to control the air flow in the main body 16. The exhaust ports19 a to 19 d are connected to an exhaust device (not shown) by flow ratecontrol valves 70 a to 70 d, respectively. The flow rate control valves70 a to 70 d are connected to an exhaust control section 71. The exhaustcontrol section 71 controls the flow rate control valves 70 a to 70 dindividually. For example, the air may be exhausted through only twoexhaust ports 19 a and 19 b, thereby causing the air to flow in aparticular direction in the main body 16. The flow of the solventevaporated from the resist solution is thereby controlled to prevent thesolvent from evaporating to excess as will be described later.

[0075] The suction table 17 has a wafer holding section 23 for holdingthe wafer 1 on the upper surface and a ZO drive mechanism 24 for drivingthe wafer holding section 23 in Zθ direction. A vacuum device (notshown) is connected to the wafer holding section 23 so that the section23 may perform vacuum chucking of the wafer 1 placed on its uppersurface. The Zθ drive mechanism 24 is connected to aZ-positioning/notch-alignment section 25 as is illustrated in FIG. 1.The Z-positioning/notch-alignment section 25 actuates the Zθ drivemechanism 24 when the wafer holder 6 moves to the wafer load/unloadsection L, making the Zθ drive mechanism 24 perform Z-directionoperation to transfer the wafer 1 and θ-operation to achieve notchalignment.

[0076] An ultrasonic vibrator 73 is secured to the wafer suction table17, for vibrating the wafer 1 held on the table 17 by virtue of vacuumsuction. The ultrasonic vibrator 73 is connected to an agitationgenerating section 74. The agitation generating section 74 appliesvibration to the wafer 1 after the wafer 1 has been coated with theresist solution. Agitation is thereby applied to the resist solutionfilm, rendering the surface of the film flat. The agitation works verywell, particularly when the resist solution is applied in asingle-stroke writing manner, because the surface of the resultant filmof resist solution is not flat in most cases unlike in the spin coatingmethod.

[0077] In the wafer holder 6, a member drive mechanism 27 is providedfor holding the mask member 4 right above the wafer 1 and for drivingthe mask member 4 in the direction of arrow A (Y direction) to move themember 4 into and from the wafer holder 6. The mask member 4 covers thewafer 1, except the circuit-forming region la, as shown in FIG. 3, andtherefore prevents the resist solution from being applied to theperipheral part of the wafer 1. The mask member drive mechanism 27 movesthe mask member 4 dirty with the resist solution, to a mask washingapparatus 42 from the resist solution applying apparatus through thepassages 38 and 39 made in the wafer holder 6 and frame 5, respectively,as is illustrated in FIG. 2.

[0078] The mask washing apparatus 42 has a washing mechanism (not shown)and holds a spare mask member 4′. The mask washing apparatus 42 receivesthe mask member 4 dirty with the resist solution, from the resistsolution applying apparatus. The spare mask member 4′, washed clean, istransported from the mask washing apparatus 42 to the resist solutionapplying apparatus. The mask member drive mechanism 27 receives the maskmember 4′ and positions the same with respect to the wafer 1.

[0079] As mentioned above, the temperature-controlled top plate 7 coversthe wafer holder 6. As shown in FIG. 1, a linear heater 26, for example,is embedded in the top plate 7 for heating the top plate 7 to apredetermined temperature. Thus heated, the top plate 7 performs twofunctions.

[0080] The first function is to maintain and control the atmosphere ofsolvent, surrounding the wafer 1. When the resist solution is applied ina manner of so-called “single-stroke writing”, it is applied in aslender stream as will be described later. The solvent contained in thesolution is therefore likely to evaporate. Hence, it is required thatthe solvent atmosphere around the nozzle unit 2 and over the uppersurface of the wafer 1 be always controlled to have a constantconcentration.

[0081] The top plate 7 is heated to the predetermined temperature, thuspreventing the solvent in the solvent atmosphere from coagulating. Inparticular, the solvent is prevented from condensing into drops on thelower surface of the top plate 7. This is how the top plate 7 controlsthe concentration of the solvent atmosphere.

[0082] The second function is to heat the nozzle unit 2 so as to preventclogging in the nozzle unit 2 and interruption of the resist solutionstream. As will be explained later in detail, the nozzle unit 2 needs toapply the resist solution in a slender stream and continuously, withoutinterruption. The discharge hole of the unit 2 is much smaller than thatof the resist solution nozzle of the conventional type. Clogging in thedischarge hole of the nozzle unit 2 must, therefore, be preventedeffectively.

[0083] The top plate 7 is located near the distal end of the nozzle unit2. Thus located, the top plate 7 heats the nozzle unit 2 and maintainthe same at an appropriate temperature, thereby effectively preventingclogging in the discharge hole of the nozzle unit 2.

[0084] Thanks to the first function, a prescribed atmosphere of solventis maintained and controlled around the nozzle unit 2. As a result, thesolvent is effectively prevented from evaporating immediately after theresist solution has been applied, thus avoiding clogging in thedischarge hole and also maintaining the resist solution at a constantviscosity. Interruption of the resist solution stream is therebyprevented.

[0085] As shown in FIG. 2, the top plate 7 is provided above the resistsolution applying section R only and covers the wafer holder 6. The topplate 7 needs to have such a size as to cover the wafer holder 6 even ifthe wafer holder 6 is moved the longest distance in the Y direction tocoat the wafer 1 with the resist solution.

[0086] As indicated above, the slit 7 a is made in the top plate 7,extending in the X direction, for allowing the nozzle unit 2 to move inthe Y direction. The slit 7 a has a length corresponding to the diameterof the wafer 1 and has a width large enough to allow passage of thenozzle unit 2.

[0087] The linear heater 26 embedded in the top plate 7 is connected toa top-plate temperature control section 28. The control section 28controls the linear heater 26.

[0088] As shown in FIG. 1, the nozzle unit 2 is held by a linear slidingmechanism 29 that stretches in the top of the frame 5 and extends in theX direction. The linear sliding mechanism 29 has an X rail 30, a slider31 slidably mounted on the X rail 30, a ball screw 32 for driving theslider 31, and an X drive motor 33 for rotating the ball screw 32.

[0089] The nozzle unit 2 is held by the slider 31 at a position where itopposes the slit 7 a made in the top plate 7. The lower end portion ofthe nozzle unit 2 extends downwards into the wafer holder 6 through theslit 7 a. It is desired that a Z drive mechanism (not shown) that candrive the nozzle unit 2 in the Z direction be provided on the slider 31to pulling the nozzle unit 2 out of the slit 7 a so that the nozzle unit2 may be regularly washed.

[0090] The X drive motor 33 for driving the nozzle unit 2 in the Xdirection and the Y drive motor 12 for driving the wafer 1 in the Ydirection are connected to a nozzle-wafer drive section 34. Thenozzle-wafer drive section 34 drives the X drive motor 33 and the Ydrive motor 12 in synchronism, thereby to move the nozzle unit 2 overthe wafer 1 in a prescribed route.

[0091] The nozzle-wafer drive section 34 operates in accordance with thesolution application route and relative speed which have been set by theroute-speed setting section 36 provided in a central control section 35.The route-speed setting section 36 determines a solution applicationroute on the basis of the wafer size (the size of the circuit-formingregion 1 a), the basic pattern of solution application route, therequired amount of resist solution to apply, and the like, which arestored in an application condition file 37.

[0092] The wafer sizes available are 6 inches, 8 inches, 12 inches, andthe like. There are various basic patterns of solution applicationroute, among which are a zigzag route (FIG. 3), a spiral route, and thelike. The amount of resist solution to apply is determined from thedesired thickness of the film and the area to coat with the resistsolution. The relative speed, which is determined from the amount ofsolution to apply and the time of applying the solution, is veryimportant because it is greatly related with the thickness of the film.

[0093] The route-speed setting section 36 may automatically set theconditions of applying the resist solution. Alternatively, an operatormay select desired conditions and input them into the route-speedsetting section 36.

[0094] The central control section 35 is a computer system foraccomplishing central control of all components of the resist solutionapplying apparatus, including those not illustrated in FIG. 1.

[0095] The nozzle unit 2 has, for example, the structure shown in FIG.4. The nozzle unit 2 has a double-pipe structure. The inner pipe is aresist solution nozzle 40 for applying the resist solution in the formof a slender stream. The outer pipe is a solvent nozzle 41 for applyinga solvent in the form of mist, along the outer circumferential surfaceof the resist solution nozzle 40.

[0096] The resist solution nozzle 40 is made of, for example, stainlesssteel. Its discharge hole 40 a has an extremely small diameter of 10 μmto 200 μm. The resist solution contains solvent, like those generallyused in this field of art. Since the discharge hole 40 a has anextremely small diameter, the ratio of its inner surface area to itsvolume is large. Consequently, the solvent is likely to evaporate,clogging the discharge hole 40 a.

[0097] To prevent the clogging effectively, the discharge hole 40 a isonly long enough to form a resist solution stream having a stablediameter, and the resist solution is supplied into the hole 40 a througha supplying hole 40 b having a relatively large diameter of, forexample, about 2 mm.

[0098] As shown in FIG. 1, the resist solution nozzle 40 is connected bya resist solution temperature control section 44 to a resist solutionsupplying section 45. To apply the resist solution in a single-strokewriting manner it is important to discharge the resist solution in astream as slender as possible, without a break, while moving the nozzleunit 2 at regular pitches, so as to form a thin film having a uniformthickness.

[0099] The maximum speed of discharging the resist solution isdetermined by the water-head pressure of the discharge hole 40 a. Todischarge the resist solution under a high pressure to attain themaximum solution-discharging speed, the resist solution supplyingsection 45 has a positive displacement pump, such as a cylinder pump,which forces out the resist solution.

[0100] Further, the resist solution applied onto the wafer 1 spreads tosome extent, depending on its viscosity. Thus, the pitch at which thenozzle unit 2 should be moved in the Y direction can be determined onthe basis of the viscosity of the solution, and the solution applicationroute is determined. Once the solution application route has beendetermined, the relative speed at which the nozzle unit 2 should bedriven is determined from the time of applying the resist solution(obtained from the solution applying rate and the amount of solution tobe discharged). In this apparatus, the relative drive speed of thenozzle unit 2 (e.g., 500 mm/s to 1 m/s) is lower than thesolution-discharging speed (e.g., 2 m/s).

[0101] In the case where the nozzle unit 2 is driven while dischargingthe resist solution, care must be taken so that a slender stream ofresist solution should not be interrupted. According to this invention,to prevent interruption of the resist solution stream, the resistsolution temperature control section 44 controls the temperature of theresist solution and the top plate 7 controls this temperature evenbefore the solution is applied. The resist solution temperature controlsection 44 is a water jacket that contains temperature-adjusting waterheated to a prescribed temperature.

[0102] The solvent nozzle 41 is connected to a solvent-temperatureadjusting/solvent supplying section 46 shown in FIG. 1. Thesolvent-temperature adjusting/solvent supplying section 46 controls thetemperature of the solvent and supplies the solvent to the solventnozzle 41. The solvent nozzle 41 applies the solvent, adjusted to apredetermined temperature, in the form of mist. As shown in FIG. 4, themist of solvent envelopes the stream of resist solution that is beingdischarged from the resist solution nozzle 40. The evaporation of thesolvent from the resist solution is thereby inhibited, maintaining theviscosity of the resist solution at a constant value and preventinginterruption of the resist solution stream.

[0103] In addition, the viscosity of the resist solution applied ontothe wafer 1 would not abruptly decrease since the wafer 1 remains in aconstant atmosphere as described above. Thus, interruption of the resistsolution stream is prevented on the wafer 1 and the spread of resistsolution is promoted.

[0104] The solvent atmosphere in the wafer holder 6 is generallycontrolled by the evaporation of solvent from the solvent channel 18,the temperature control achieved by the top plate 7, and the dischargeof solvent mist from the solvent nozzle 41. (Namely, an atmospherecontrol mechanism is provided according to the present invention.) Thiscontrol of the solvent atmosphere is managed by an atmosphere managementsection 47 provided in the central control section 35.

[0105] The step of applying the resist solution, performed by thisresist solution applying apparatus, will be explained next.

[0106] (1) First, a semiconductor wafer 1 is loaded into the resistsolution applying apparatus. The Y drive motor 12 is driven, positioningthe wafer holder 6 at the wafer load/unload section L located at theother end of the frame 5.

[0107] The wafer 1 is transferred to the wafer load/unload section L,while held by the main arm (not shown) provided for transferring wafers.The Zθ drive mechanism 24 is actuated, moving the wafer holding section23 of the wafer suction table 17, up or down, whereby the wafer 1 isplaced onto the wafer suction table 17. Then, the suction mechanism (notshown) is actuated, whereby the wafer suction table 17 holds the wafer 1by virtue of a suction force.

[0108] Now that the wafer 1 held by virtue of a suction force, notchalignment is achieved by the Z-positioning/notch-alignment section 25. Alight-emitting device and a light-receiving sensor are arranged on theframe 5, at specific positions where they oppose the peripheral part ofthe wafer 1. The Zθ drive mechanism 24 rotates the wafer 1. Themechanism 24 stops the wafer 1 the moment the light-receiving sensordetects the notch 1 b (FIG. 3) made in the peripheral part of the wafer1, that is, after the wafer 1 has rotated through an angle. When notchalignment is thus accomplished, the wafer holding section 23 is drivendownwards, and the wafer 1 is moved into the wafer holder 6. In thewafer holder 6 the wafer 1 is locked not to rotate.

[0109] Next, the Y drive motor 12 is driven, moving the wafer holder 6and positioning the same at the resist solution applying section R.After the wafer holder 6 has been positioned at the resist solutionapplying section R, the mask member drive mechanism 27 receives the maskmember 4 from the mask washing apparatus 42 and holds the mask member 4above the wafer 1.

[0110] (2) While the wafer 1 being loaded, the atmosphere managementsection 47 provided in the central control section 35 keeps managing thesolvent atmosphere. That is, the solvent in the solvent channel 18 ofthe wafer holder 6 has already been controlled in temperature andsurface level. Further, the top plate 7 has been heated to a prescribedtemperature, thus preheating the nozzle unit 2. Still further, thesolvent is discharged from the solvent nozzle 41, preventing the resistsolution from drying in the discharge hole 40 a of the resist solutionnozzle 40 and, hence, avoiding clogging of the discharge hole 40 a.

[0111] (3) When the wafer 1 is positioned at the resist solutionapplying section R, the central control section 35 causes the nozzleunit 2 and the wafer 1 to move relative to each other in accordance withthe solution application route, relative drive speed and otherconditions which have been set by the route-speed setting section 36,thereby applying the resist solution to the wafer 1.

[0112] To move the nozzle unit 2 along the route shown in FIG. 3, it isnecessary to decelerate and accelerate the nozzle unit 2 at each turningpoint in the X direction. This may result in variation in the thicknessof resist solution film. In order to avoid such variation, the nozzleunit 2 is turned back above the mask member, that is, outside thecircuit-forming region la of the wafer 1. Thus, the nozzle unit 2 ismoved at a constant speed over the entire the circuit-forming region la.

[0113] The film of the resist solution applied onto the wafer 1 isthereby adjusted in accordance with the diameter of the solution stream,the relative speed of the nozzle unit 2 and the spread of the resistsolution on the wafer 1. As a result, a solution film having a uniformthickness is formed on the circuit-forming region 1 a of the wafer 1.

[0114] At this time, the exhaust control section 71 operates,controlling the airflow around the wafer 1, thereby inhibiting theevaporation of solvent from the resist solution applied to the wafer 1.To move the nozzle unit 2 in the Y direction, for example, from the leftto the right in FIG. 2, air is exhausted through only the exhaust ports19 a and 19 b provided at the upstream in the Y direction, not throughthe other exhaust ports 19 a and 19 d. The solvent evaporated from theresist solution is thereby guided to the resist solution already appliedto the wafer 1, whereby a solvent atmosphere covers the surface of theresist solution film. This effectively prevents the solvent fromevaporating to excess from the resist solution already applied to thewafer 1.

[0115] After the application of resist solution has completed, theagitation generating section 74 actuates the ultrasonic vibrator 73secured to the wafer suction table 17. The vibrator 73 vibrates thewafer 1 at a frequency of the ultrasonic frequency band. The resistsolution applied to the wafer 1 is thereby agitated, whereby the surfaceof the solution film become flat.

[0116] (4) Upon completion of the above-mentioned sequence ofoperations, the mask member 4 got dirty with the resist solution isejected into the mask washing apparatus 42. Then, the wafer holder 6 ismoved away from the resist solution applying section R to the waferload/unload section L. At the wafer load/unload section L, the waferholding section 23 is moved up or down, thereby transferring the wafer 1to the main arm (not shown).

[0117] The structure described above can be advantageous in thefollowing respects.

[0118] First, the use efficiency of resist solution can be muchincreased to, in some cases, nearly 100% since the resist solution isapplied in a single-stroke writing manner, without rotating the wafer 1.

[0119] In the spin coating method, generally employed as a method ofapplying resist solution, the resist solution is spun off in dropletsfrom the peripheral part of the wafer, inevitably wasted in a largeamount, because the wafer is rotated at high speed. In one instance,only 10% of the resist solution applied onto the wafer contributes tothe formation of a resist film.

[0120] In this method, the resist solution may be applied also to theperipheral part of the wafer, in which no circuits will be formed. Theresist solution applied to this region usually needs to be removed by adedicated apparatus called “edge remover,” immediately after the step ofapplying the resist solution.

[0121] By contrast, the resist solution need not be removed after thestep of applying the resist solution in the resist solution applyingapparatus according to this invention. This is because the useefficiency of resist solution is greatly increased in the apparatusaccording to the invention.

[0122] Second, interruption of the resist solution stream can beprevented, making it possible to form a film of solution that is thinand uniform.

[0123] That is, to apply resist solution is applied in a single-strokewriting manner, it is necessary to apply the solution in the form of asslender a stream as possible and to prevent the stream of the solutionfrom being interrupted. Further, it is probable that the stream ofsolution is interrupted if the solution changes in its viscosity whilebeing discharged. It is also probable that the solution-applying nozzleis clogged. These undesired events should be prevented, too.

[0124] With this invention it is possible to control, with highprecision, the concentration of the solvent atmosphere that envelops thestream of resist solution, in order to prevent interruption of thestream of resist solution. Hence, the viscosity of the stream can bemaintained constant, however slender the stream is. Thus, the stream ofresist solution can be prevented from being interrupted.

[0125] Particularly, the solvent can be prevented from evaporating fromthe resist solution and from changing in terms of viscosity evenimmediately after the resist solution has been discharged from thenozzle unit 2. This is because the solvent nozzle 41 provided is madeintegral with the nozzle unit 2. Further, interruption of the stream ofresist solution can be prevented by controlling, with high precision,the concentration of the solvent atmosphere and the heating of thenozzle unit 2 by the use of the top plate 7.

[0126] Third, since the resist solution can be prevented from spinningoff in droplets, forming of particles can be effectively prevented.

[0127] That is, in the spin coating method, the wafer must be rotated ina cup so that the cup may receive the resist solution spinning off indroplets from the wafer. The solution sticking to the cup formparticles, which may contaminate the wafer. It is therefore necessary towash the cup frequently.

[0128] By contrast, in the resist solution applying apparatus accordingto this invention, the stream of resist solution, which is applied at atime, can have a very small diameter, preventing the solution fromleaving the wafer. In addition, since the wafer 1 is not rotated, thesolution scarcely spins off in droplets. Such a cup as is required inthe spin coating method need not be provided. Nor will it be necessaryto wash such a cup.

[0129] Fourth, the mask member 4 covers the peripheral part of the wafer1, and the nozzle unit 2 starts and stops applying the resist solutionand repeatedly changes its moving direction only while it is movingabove the mask member 4. Thus, the nozzle unit 2 can be moved at aconstant speed, that is, neither accelerated nor decelerated whilemoving over the circuit-forming region 1 a of the wafer 1. This helpsform a resist solution film having a uniform thickness.

[0130] In this case, the mask member 4 gets dirty with the resistsolution. Nevertheless, the mask member 4 can be washed since the maskwashing apparatus 42 is provided beside the resist solution applyingapparatus. Further, the throughput of applying the resist solution wouldnot be reduced because the mask washing apparatus 42 moves the maskmember 4′, already washed, to the position above the wafer 1, at thesame time it receives the mask member 4, got dirty with the solution,from that position.

[0131] Fifth, the apparatus of the invention can reliably apply theresist solution to the entire circuit-forming region 1 a of the wafer 1.This renders it unnecessary to perform a pre-wetting step (i.e.,applying a solvent, such as thinner, to the surface of the wafer 1before applying the resist solution thereto). The film-forming step canbe thereby simplified.

[0132] (Coating/Developing System)

[0133] It is desirable to apply this resist solution applying apparatusto the coating/developing system shown in FIGS. 5 to 7.

[0134] As shown in FIG. 5, the coating/developing system comprises acassette section 50, a process section 51, and an interface section 52.In the cassette section 50, wafers 1 are sequentially taken from acassette CR. In the process section 51, the resist solution is appliedto a wafer 1 and the resist film formed on the wafer 1 is developed. Atthe interface section 52, the wafer 1 coated with the resist solution istransferred to and from an exposure apparatus (not shown).

[0135] The cassette section 50 comprises four projections 60 a forpositioning and holding cassettes CR and a first sub-arm mechanism 61for taking a wafer 1 from the cassette CR held by any projection 60 a.The sub-arm mechanism 61 can rotate the wafer 1 in direction, thuschanging the orientation of the wafer 1 and also can transfer the wafer1 to a main arm mechanism 62 provided in the process section 51.

[0136] Wafers 1 are transferred between the cassette section 50 and theprocess section 51 through the process units of a third group G3. Asshown in FIG. 7, the process units of the third group G3 are arrangedone upon another, forming a vertical column. More precisely, the thirdprocess unit group G3 is composed of a cooling unit (COL) for cleaning awafer 1, an adhesion unit (AD) for rendering the wafer 1 hydrophobic tobe well wetted with resist solution, an alignment unit (ALIM) foraligning the wafer 1, an extension unit (EXT) for holding the wafer 1 ata wait position, two pre-baking unit (PREBAKE) for heating the wafer 1before exposure process, and two post-baking units (POBAKE) for heatingthe wafer 1 after the exposure process, which are arranged one onanother in the order they are mentioned.

[0137] The wafer 1 is transferred to the main arm mechanism 62 throughthe extension unit (EXT) and the alignment unit (ALIM).

[0138] As shown in FIG. 5, the first to fifth process unit groups G1 toG5 of process units, including the third process unit group G3, surroundthe main arm mechanism 62. Like the third process unit group G3, theother process unit groups G1, G2, G4 and G5 are each composed of severalunits arranged one upon another.

[0139] Two resist solution applying apparatuses (COT) according to thisinvention are included in the first process unit group G1 and the secondprocess unit group G2, respectively, as is illustrated in FIG. 6. Twodeveloping apparatuses (DEV) are mounted on the resist solution applyingapparatuses (COT), respectively.

[0140] As shown in FIG. 7, the main arm mechanism 62 comprises a hollowcylindrical guide 69 that extends vertically and a main arm 68 that canbe driven vertically along a guide 69. The main arm 68 can also rotatein a horizontal plane and can be driven back and forth. Thus, when themain arm 68 is moved up or down, a wafer 1 can have access to anyprocess unit provided in any one of the process unit groups G1 to G5.

[0141] The main arm mechanism 62 receives a wafer 1 from the cassettesection 50 through the extension unit (EXT) of the third process unitgroup G3 and transports the wafer 1 into the adhesion unit (AD) of thethird process unit group G3. In the adhesion unit (AD) the wafer 1 isrendered hydrophobic. Then, the mechanism 62 transports the wafer 1 fromthe adhesion unit (AD) into the cooling unit (COL), in which the wafer 1is cooled.

[0142] The wafer 1, thus cooled, is made to oppose the resist applyingapparatus (COT) of the first process unit group G1 (or second processunit group G2) and is moved into this resist applying apparatus (COT).The wafer 1 can be thereby loaded into the wafer load/unload section Lof the resist applying apparatus according to the present invention.

[0143] In the resist applying apparatus (COT), resist solution isapplied on the wafer 1 in a single-stroke writing manner as describedabove. The main arm mechanism unloads the wafer 1 from the waferload/unload section L and transfers the wafer 1 to the interface section52 through the fourth press unit group G4.

[0144] As shown in FIG. 7, the fourth process unit group G4 comprises acooling unit (COL), an extension/cooling unit (EXT/COL), an extensionunit (EXT), a cooling unit (COL), two pre-baking units (PREBAKE), andtwo postbacking units (POBAKE), which are arranged one upon the other inthe order they are mentioned.

[0145] The wafer 1 taken from the resist applying apparatus (COT) isfirst inserted into the pre-baking unit (PREBAKE), in which the solvent(thinner) is evaporated from the resist solution, thus drying the wafer1. The drying of wafer may be accomplished by, for example, vacuumdrying method. That is, the wafer 1 is inserted into the pre-baking unit(PEBAKE) or a chamber other than the pre-baking unit, and the pressuretherein may be reduced to remove the solvent (or to dry the resistsolution).

[0146] Note that, the pre-baking unit (PREBAKE) for drying the wafer 1may be located inside the resist applying apparatus (COT).

[0147] Next, the wafer 1 is cooled in the cooling unit (COL) andtransferred via the extension unit (EXT) to a second sub-arm mechanism54 that is provided in the interface section 52.

[0148] The second sub-arm mechanism 54 holds the wafers 1 it has'received, into the cassette CR, one after another. The interface section52 transfers the cassette CR containing the wafers 1, to the exposureapparatus (not shown), and receives the cassette CR containing thewafers 1 which have undergone the exposure process.

[0149] Each wafer 1 subjected to the exposure process is transferred viathe process units of the fourth group G4 in the reverse order, to themain arm mechanism 62. The main arm mechanism 62 inserts the wafer 1,which has been exposed to light, into the post-baking unit (POBAKE), ifnecessary. Then, the mechanism 62 inserts the wafer 1 into thedeveloping apparatus (DEV), in which the wafer 1 is subjected todeveloping process. The wafer 1, which has undergone the developingprocess, is transported to any baking unit, heated and dried therein,and transferred to the cassette section 50 through the extension unit(EXT) of the third process unit group G3.

[0150] The fifth process unit group G5 is selectively provided. In thepresent instance, it is composed in the same way as the fourth processunit group G4. The fifth process unit group G5 is movably supported onrails 55, thereby facilitating the maintenance of the first to fourthprocess unit groups G1 to G4.

[0151] If the film forming apparatus according to the invention is usedin the coating/developing system shown in FIGS. 5 to 7, a plurality ofwafers can be processed simultaneously, whereby the coating/developingstep can be conducted on the wafers 1 with high efficiency. In addition,the installation area for the system can be remarkably reduced becausethe process units are arranged, one upon another, forming verticalcolumns.

[0152] The film forming apparatus according to the first embodiment canbe, of course, used in systems other than the coating/developing systemdescribed above. Moreover, the film forming apparatus can be modified invarious ways, within the scope of the present invention.

[0153] First, the resist-solution applying nozzle unit 2 is not limitedto the one illustrated in FIG. 4. Rather, the structure 2′ shown in FIG.8, for example, may be used instead. In FIG. 8, the components identicalto those shown in FIG. 4 are designated at the same reference numerals.

[0154] The nozzle unit 2′ is of double-pipe structure like the nozzleunit 2 of FIG. 4. The inner pipe is a resist solution nozzle 40 forapplying the resist solution in the form of a slender stream, and theouter pipe is a solvent nozzle 41 for applying a solvent in the form ofmist. However, a solvent pan 70 is provided at the lower end of thesolvent nozzle 41, for accumulating the solvent.

[0155] This structure can not only attain the same advantages as thenozzle unit 2 of FIG. 4, but also minimize the changes in the atmosphereof solvent. In other words, the atmosphere of solvent stabilizes.

[0156] Second, the solution application route is not limited to thatadopted in the first embodiment (FIG. 3). Rather, it may be such aspiral one as is shown in FIG. 9. If this is the case, it is preferablethat the nozzle unit 2 be moved in the radial direction of the wafer 1(e.g., the X direction) while rotating the wafer 1 at low speed (e.g.,20 to 30 rpm).

[0157] In this case, too, it is important to maintain the speed of thewafer 1, relative to the nozzle unit 2, at a constant value. If thenozzle unit 2 is moved at a constant speed, for example, the rotationspeed of the wafer 1 must be gradually lowered as the nozzle unit 2approaches the peripheral edge of the wafer 1. On the other hand, if thewafer is rotated at a constant speed, the speed of the nozzle unit 2must be gradually lowered as the nozzle unit 2 moves toward theperipheral edge of the wafer 1.

[0158] Third, to form a film of resist solution, which has a uniformthickness, the resist solution may be applied twice to the wafer 1,first in a first direction and then in a second direction, as isillustrated in FIG. 10. In this case, both the point START at which theapplication of solution is started and the point END at which theapplication of solution is terminated are located above the mask member7. Thus, the nozzle unit 2 can be moved always at a constant speed overthe wafer 1, thereby forming a film of resist solution that has auniform thickness.

[0159] Fourth, in the first embodiment described above, the wafer 1 isintermittently moved in the Y direction at a certain pitch and thenozzle unit 2 is driven back and forth in the X direction. The method ofmoving the wafer 1 and nozzle unit 2 is not limited to this one.Instead, the wafer 1 may be moved in the X and Y directions, while thenozzle unit 2 is retained at a fixed position. In this case, the topplate 7 need not have a slit 7 a, which enhances the insulationeffectiveness.

[0160] Further, the actual mechanisms for driving the nozzle unit 2 andwafer holder 6 are not limited to those used in the first embodiment.Needless to say, other drive mechanisms, such as belt drive mechanisms,may be employed instead.

[0161] Fifth, any solution other than the resist solution used in thefirst embodiment may be applied to the wafer 1 to form a film thereon.For example, a solution for forming an interlayer insulating film, asolution for forming a highly conductive film, a ferroelectric solution,sliver paste, or the like may be applied in place of the resistsolution.

[0162] Sixth, the substrate to be processed is a semiconductor wafer 1in the embodiment described above. Nonetheless, the substrate may be anLCD substrate or an exposure mask.

[0163] Further, although one nozzle unit is used in the above-describedembodiment, two or more nozzle units may be arranged side by side. Ifso, it is possible to shorten the time for coating the wafer 1 with theresist solution.

[0164] Seventh, the mask member 4 used in the first embodiment may notbe used. In this case, it suffices to provide a container, such as acup, below the wafer 1, to receive the residual resist solution.

[0165] Eighth, the technique of agitating the film of resist solution toimpart a flat surface thereto is not limited to the method performed inthe first embodiment, i.e., the use of the ultrasonic vibrator 73secured to the wafer suction table 17.

[0166] For example, no vibrator may be used, and the wafer 1 may bemoved in the Y direction by means of a ratchet mechanism, thereby toagitate the solution film formed on the wafer 1. Alternatively, anyother method may be employed to agitate the solution film formed on thewafer 1.

[0167] Ninth, the mask member 4 having an opening exposing thecircuit-forming region 1 a of the wafer may be moved in the Y directionalong with the nozzle unit 2, not retained immovable with respect to thewafer 1 as in the first embodiment described above.

[0168] In this case, the mask member must be one whose opening changesin size in accordance with the back-and-forth stroke of the nozzle unit2 moving in the X direction. For instance, a mask member 80 of thestructure illustrated in FIG. 11A may be employed.

[0169] The mask member 80 shown in FIG. 11A has a pair of solution pans81 that are spaced apart in the X direction. The solution pans 81 can bedriven to change the distance between them, in accordance with theX-direction stroke of the nozzle unit 2. Thus, the pans 81 are locatedalways at the two turning points of the nozzle unit 2, respectively.

[0170] That is, the solution pans 81 are connected to a pan-drivingmechanism 82 by L-shaped arms 83. The pan-driving mechanism 82 issecured to the linear sliding mechanism 29 shown in FIG. 2 and can movein the Y direction together with the linear sliding mechanism 29. Thepan-driving mechanism 82 may comprise, for example, a stepping motor anda linear gear.

[0171] The pan-driving mechanism 82 is also connected to the centralcontrol section 35 and operates in accordance with the solutionapplication route and the relative speed, both set by the route-speedsetting section 36. That is, the distance between the solution pans 81is controlled to a value substantially equal to the X-direction strokeof the nozzle unit 2, i.e., the width of the circuit-forming region 1 a.

[0172] The solution pans 81 have, for example, the structure shown inFIGS. 11B and 11C. FIG. 11B is a vertical sectional view, and FIG. 11Cis a front view.

[0173] Each solution pan 81 has a channel-shaped main body 85 that opensat the top. The main body has two side walls 85 a, which stand from theupper surface of the main body 85 and which extend in the Y direction.The walls 85 a prevent the resist solution from dripping from the longsides of the solution pan 81. No walls stand from the distal end of themain body 85. The distal end of the main body 85 is inclined downwardsand toward the proximal end of the main body 85, forming an inclinedsurface 85 b. The main body 85 has a first suction hole 86, which opensat the inclined surface 85 b to draw the resist solution, which mayotherwise drip along the inclined surface 85 b.

[0174] The upper surface of the main body 85 is gently inclineddownwards to the proximal end. The proximal end of the main body 35 hasa second suction hole 87 through which the resist solution can be drawnfrom the upper surface of the main body 85.

[0175] The first and second suction holes 86 and 87 are connected tosolution discharge tubes 88 and 89, respectively. The resist solutionthe solution pan 81 has received is forcedly discharged.

[0176] The solution pans 81 may be washed with solvent, such as thinner,in the frame 5 or the cup-shaped main body 16.

[0177] The mask member 80 shown in FIG. 11A is smaller than the maskmember used in the first embodiment described above and can be washedwithin the apparatus. Hence, the mask member 80 serves to miniaturizethe apparatus as a whole.

[0178] The mechanism for driving the solution pans 81 is not limited tothe one depicted in FIG. 11A. For example, the distance between the pans81 may be adjusted by using, as shown in FIG. 11D, a guide plate 90 inwhich two profiling cams 91 are cut. Each profiling cam 91 has the sameshape as the peripheral edge of the circuit-forming region 1 a of thewafer 1. The two cam followers 92 protrude downwards from the pans 81are inserted in the profiling cams 91. The cam followers 92 are drivenalong the profiling cams 91, respectively, whereby the distance betweenthe solution pans 81 is controlled.

[0179] (Second Embodiment)

[0180] The second embodiment of the present invention will be described,with reference to FIGS. 12 to 17. The second embodiment is a resistsolution applying apparatus, which is preferably used also in thecoating/developing system illustrated in FIGS. 5 to 7. Thecoating/developing system will not be described below since it has beendescribed above in detail.

[0181] The film forming apparatus according to this embodiment is thesame as the first embodiment in that resist solution 3 is applied toonly the circuit-forming region 1 a of a wafer 1 in a so-calledsingle-stroke writing manner as illustrated in FIG. 12.

[0182] In the second embodiment, however, the wafer 1 is turned upsidedown and held, with the circuit-forming region 1 a facing downwards asshown in FIG. 12, and the resist solution 3 is discharged upwards from asolution applying nozzle unit 2 to coat the region 1 a with the resinsolution.

[0183] Also in this embodiment, a mask member 4 is arranged right belowthe wafer 1, covering the peripheral part of the wafer 1, not coveringthe circuit-forming region 1 a. The solution applying nozzle unit 2 isdriven back and forth in the X direction, while being intermittentlymoved in the Y direction at a certain pitch, thereby coating only thecircuit-forming region 1 a with the resist solution.

[0184] The structure of this resist applying apparatus, which is a filmforming apparatus, will be described below in detail.

[0185]FIGS. 13A and 13B are partial sectional views of the resistapplying apparatus, and FIG. 14 is a plan view thereof.

[0186] As shown in FIG. 14, this apparatus has a main arm mechanism 110,a reversing mechanism 111 for turning upside down the wafer 1transported by the main arm mechanism 110, a sub-arm mechanism 112 forreceiving the wafer 1 thus turned and transport the same in thedirection of arrow a, a solution applying mechanism 113 for applyingresist solution to the wafer 1 transported by the sub-arm mechanism 112and held at a predetermined position, and a mask member washingmechanism 113 for removing the mask member 4 from the resist solutionapplying mechanism 113 and washing the mask member 4.

[0187] As shown in FIG. 13A, the resist solution applying mechanism 113has a frame 116 and a nozzle unit drive mechanism 117 provided in theframe 116, for driving the nozzle unit 2 in X, Y and Z directions. Thenozzle unit 2 is arranged, with the discharge port turned upwards, andopposes the wafer 1 held by the sub-arm mechanism 112.

[0188] The sub-arm mechanism 112 holds the wafer 1 as is illustrated inFIG. 13B. The sub-arm mechanism 112 has a pair of arms 120 that can openand close in the direction of arrow 113 (FIG. 13B) and holding pads 121secured to the inner surfaces of the arms 120, for holding the wafer 1without touching the circuit-forming region 1 a of the wafer 1. Forexample, four holding pads 121 are arranged along the circumference ofthe circle defined by the arms 120, as is illustrated in FIG. 14.

[0189] The frame 116 is shaped as shown in FIG. 13A, defining a space inwhich the nozzle unit 2 can move. A solvent channel 122 is provided inthis space so that a solvent atmosphere may envelop the nozzle unit 2.The solvent channel 122 is filled with solvent that is controlled intemperature and surface level. The solvent evaporates, forming a solventatmosphere having a predetermined concentration and enveloping the wafer1. The above-mentioned mask member 4 is removably held at the top of theframe 116.

[0190] The nozzle unit drive mechanism 117 has a Y-direction drivemechanism 125 secured to the lower surface of the frame 116, anX-direction drive mechanism 126 held by the Y-direction drive mechanism125 and able to move in the Y direction, and a Z-direction drivemechanism 127 held by the X-direction drive mechanism 126 and able tomove in the Z direction. The nozzle unit 2 is attached to theZ-direction drive mechanism 127 and can be moved in the X, Y and Zdirections to be positioned. The drive mechanisms 125 to 127 may be ofany appropriate type. They may be ball-screw drive mechanisms or beltdrive mechanisms.

[0191] As illustrated in FIG. 14, one end portion of the Y-directiondrive mechanism 125 extends toward the lower end of the diagram, fromthe space where the resist solution is applied. The Y-direction drivemechanism 125 is designed to drive the nozzle unit 2 and position thesame at a nozzle unit station 129.

[0192]FIG. 15 shows the nozzle unit 2 held at the nozzle unit station129. With reference to FIG. 15, the structures of the nozzle unit 2 andnozzle unit station 129 will be described.

[0193] The nozzle unit 2 comprises a nozzle 130 and a nozzle holder 131holding the proximal end of the nozzle 130.

[0194] The nozzle 130 is made of, for example, stainless steel. Itsdischarge hole 130 a has an extremely small diameter of 10 μm to 200 μm.The resist solution to be discharged from the hole 130 a containssolvent, like those generally used in this field of art. Since thedischarge hole 130 a has an extremely small diameter, the ratio of itsinner surface area to its volume is large. Consequently, the solvent islikely to evaporate, clogging the discharge hole 130 a.

[0195] To prevent the clogging effectively, the discharge hole 130 a isonly long enough to form a resist solution stream having a stablediameter, and the resist solution is supplied into the hole 130 athrough a supplying hole 130 b having a relatively large diameter of,for example, about 2 mm.

[0196] The nozzle holder 131 has a resist solution passage 133 thatconnects the nozzle 130 and a resist solution pipe 132. Further, thenozzle holder 131 has a solvent bypass passage 134 for supplying asolvent such as thinner into the nozzle 130.

[0197] The bypass passage 134 is opened while the nozzle unit 2 is heldat the nozzle unit station 129. Thus, the solvent is continuously passedthrough the discharge hole 130 a of the nozzle 30, thereby preventingclogging of the discharge hole 130 a. The solvent discharged from thenozzle 130 evaporates in the nozzle unit station 129, forming a solventatmosphere of a prescribed concentration, which envelops the distal endof the nozzle 130.

[0198] The nozzle unit station 129 has a nozzle insertion hole 136 intowhich the distal end of the nozzle 130 can be inserted. In the nozzleunit station 129 a solvent channel 137 is provided to receive thesolvent discharged from the nozzle 130. The solvent accumulated in thesolvent channel 137 is sequentially drained through a draining pipe 138.

[0199] Next, this resist solution applying apparatus will be describedwith reference to FIG. 15.

[0200] First, the resist solution pipe 132 is connected to a resistsolution supplying section 142. A solution supply valve 140 and a resistsolution temperature control section 141 are provided on the resistsolution pipe 132.

[0201] When the resist solution is applied in a manner of single-strokewriting, it is important to discharge the solution in as slender astream as possible and in a stable and continuous state, without break,in order to form a thin film having a uniform thickness.

[0202] The maximum speed of discharging the resist solution isdetermined by the water-head pressure in the discharge hole 130 a. Todischarge the resist solution under a high pressure to attain themaximum solution-discharging speed, the resist solution supplyingsection 142 has a positive displacement pump, such as a cylinder pump,which forces out the resist solution.

[0203] Further, the resist solution applied onto the wafer 1 spreads tosome extent, depending on its viscosity. Thus, the pitch at which thenozzle unit 2 should be moved in the Y direction can be determined onthe basis of the viscosity of the solution, and the solution applicationroute is determined. Once the solution application route has beendetermined, the relative speed at which the nozzle unit 2 should bedriven is determined from the time of applying the resist solution(obtained from the solution applying rate and the amount of solution tobe discharged). In this apparatus, the relative drive speed of thenozzle unit 2 (e.g., 500 mm/s to 1 m/s) is lower than thesolution-discharging speed (e.g., 2 m/s).

[0204] In the case where the nozzle unit 2 is driven while dischargingthe resist solution, the solvent may evaporate and the solution may bedried at its surface, possibly causing interruption of the solutionstream. To prevent this, the resist solution is discharged to the lowersurface of the wafer 1. The solvent evaporates and rises upwards. Inthis embodiment, the wafer 1 serves as a cover, inhibiting theevaporation of prevented, whereby interruption of the solution streamcan be effectively avoided.

[0205] To prevent interruption of the resist solution streameffectively, the resist solution temperature control section 141controls the temperature of the resist solution. The resist solutiontemperature control section 141 is a water jacket that containstemperature-adjusting water heated to a prescribed temperature.

[0206] The system for supplying the solvent comprises a solvent pipe143, a solvent valve 144 connected to the bypass passage 134, a solventtemperature control section 145, and a solvent supplying section 146.

[0207] The solvent valve 144 is a passage control valve. The valve 144is closed while the resist solution is being applied. It is opened onlywhile no resist solution is being applied, continuously passing thesolvent, which is controlled in temperature and concentration, throughthe discharge hole 130 a of the nozzle 130.

[0208] The solution supply valve 140, resist solution temperaturecontrol section 141, resist solution supplying section 142, solventvalve 144, solvent temperature control section 145 and solvent supplyingsection 146 are connected to and controlled by a central controlsection.

[0209] The central control section 147 is the computer which controlsall components of this resist solution applying apparatus, not only thecomponents shown in FIG. 15 but also those not illustrated in FIG. 15.

[0210] A nozzle unit driver 149 for operating the nozzle unit drivemechanism 117 which comprises the X-, Y- and Z-direction drivemechanisms and the like, a sub-arm mechanism driver 150 for controllingthe sub-arm mechanism 112, and a reversing mechanism driver 151 forcontrolling the reversing mechanism 111 are connected to the centralcontrol section 147.

[0211] The nozzle unit driver 149 operates in accordance with thesolution application route and the relative speed, both set by aroute-speed setting section 152 incorporated in the central controlsection 147. The route-speed setting section 152 has determined thesolution application route on the basis of the wafer size (the size ofthe circuit-forming region 1 a), the basic pattern of solutionapplication route, the required amount of resist solution to apply, andthe like, which are stored in an application condition file 148.

[0212] The wafer sizes available are 6 inches, 8 inches, 12 inches, andthe like. There are various basic patterns of solution applicationroute, among which is a zigzag route (FIG. 12), a spiral route, and thelike. The amount of resist solution to apply is determined from thedesired thickness of the film and the area to coat with the resistsolution, because the use efficiency of resist solution is nearly 100%in this apparatus. The relative speed, which is determined from theamount of solution to apply and the time of applying the solution, isvery important because it is greatly related with the thickness of thefilm.

[0213] The conditions of applying resist solution may be automaticallyset the conditions of applying the resist solution. Alternatively, anoperator may select desired conditions and input them into theroute-speed setting section 152.

[0214] The sub-arm mechanism driver 150 drives the sub-arm mechanism 112in the direction of the arrow shown in FIG. 14, closes the arms 120 tochuck the wafer 1, and opens the arms 120 to unchuck the wafer 1.

[0215] As indicated above, the sub-arm mechanism 112 can hold the wafer1, without touching the lower surface of the wafer 1. It receives thewafer 1 at the reversing mechanism 111, transports the wafer 1 to aposition above the resist solution applying mechanism 113, and holds thewafer 1 at this position. When the wafer 1 is coated with the resistsolution, sub-arm mechanism 112 takes the wafer 1 from the resistsolution applying mechanism 113 and transfers the wafer 1 back to thereversing mechanism 111.

[0216]FIG. 16 is a schematic view showing an example of the reversingmechanism 111.

[0217] This reversing mechanism 111 has a wafer holding mechanism 153.The wafer holding mechanism 153 has a ZO drive mechanism 154 and waferholding arms 155 connected to the ZO drive mechanism 154. Pins 156protrude upwards from the distal end of each wafer holding arm 155. Thepins 156 can touch the peripheral part of the wafer 1, i.e., the partoutside the circuit-forming region 1 a of the wafer 1.

[0218] Above the wafer holding mechanism 153, a reversing arm mechanism158 is provided for turning the wafer 1 upside down. The reversing armmechanism 158 is similar in structure to the sub-arm mechanism 112 (FIG.13B). It has arms 157 that can be opened and closed and holding pads 159that can hold the wafer 1 without touching the circuit-forming region 1a thereof.

[0219] The arms 157 are held by a drive unit 160 that is designed todrive the reversing arm mechanism 158. When driven by the drive unit160, the arms 157 turn the wafer 1 upside down, through 180°.

[0220] It will be described below how the reversing mechanism 111operates, for example, to transfer the wafer 1 from the main armmechanism 110 to the sub-arm mechanism 112.

[0221] First, the main arm mechanism 110 holding the wafer 1 movestoward the wafer holding mechanism 153 of the reversing mechanism 111,thus positioning the wafer 1 right above the wafer holding arms 155.Next, the wafer holding mechanism 153 moves the wafer holding arms 155upwards, whereby the wafer 1 is placed on the upper surfaces of the arms155.

[0222] Since the lower surface of the wafer 1 is not coated with resistsolution, the wafer 1 may be held at the central part of its lowersurface. Thus, the wafer 1 may be transferred from onto the waferholding arms 155 by being first held at its center part, then elevatedfrom the main arm mechanism 110, and finally lowered.

[0223] Next, the wafer holding arms 155 are moved up to the level wherethe arms 157 of the reversing arm mechanism 158. The arms 157 areclosed, clamping the wafer 1 and the wafer holding arms 155 are moveddownwards. Thus, the wafer 1 is transferred from the arms 157 of thereversing arm mechanism 158.

[0224] Then, the drive unit 160 of the reversing arm mechanism 158 isoperated, reversing the wafer 1 upside down.

[0225] After the wafer 1 has been reversed, the wafer holding arms 155are moved upwards again to take the wafer 1, thus reversed, from thewafer holding mechanism 153. At this time, the pins 156, which protrudefrom the distal end of the arms 155 hold the wafer 1.

[0226] Further, the wafer holding arms 155 are lowered to the levelwhere the sub-arm mechanism 112 is located. Before the wafer 1 istransferred to the sub-arm mechanism 112, the Zθ drive mechanism 154 isoperated, achieving the notch alignment of the wafer 1.

[0227] Upon completion of the notch alignment, the wafer 1 istransferred to the sub-arm mechanism 112. The sub-arm mechanism 112transports the wafer 1 to the resist solution applying mechanism 113 andpositions the wafer 1 right above this mechanism 113.

[0228] Having the structure described above, the reversing arm mechanism158 can reverse the wafer 1, without touching the circuit-forming region1 a of the wafer 1.

[0229] A mask member washing mechanism 114 is provided beside the resistsolution applying mechanism 113. The mechanism 114 will be describedbelow.

[0230] As shown in FIG. 1, the mask member 4 covers all upper surface ofthe wafer 1, except the circuit-forming region 1 a, thus preventing theperipheral part of the wafer 1 from being coated with the resistsolution. Hence, the mask member 4 is inevitably got dirty with theresist solution and should be regularly washed.

[0231] The mask member 4 dirty with the resist solution is removed fromthe resist solution applying mechanism 113 through an insertion/ejectionpath (not shown) and moved into mask member washing mechanism 114.

[0232] The mask member washing mechanism 114 holds a spare mask member4′. The mask washing mechanism 114 receives the mask member 4 dirty withthe resist solution, from the resist solution applying apparatus, andtransports the spare mask member 4′, washed clean, to the resistsolution applying apparatus. The mask member washing mechanism 114 thenwashes the mask member 4 got dirty.

[0233] The step of applying the resist solution, performed by the resistsolution applying apparatus, will be explained with reference to theflow chart of FIG. 17. The operations already detailed above will not bedescribed in detail.

[0234] (1) Loading of the Wafer (Steps S1 to S5)

[0235] At first, the wafer 1 is loaded from the main arm mechanism 110into the reversing mechanism 111 (Step SI). Then, the reversingmechanism 111 reverses the wafer 1 in the way described above (Step S2).

[0236] Next, the notch alignment of the wafer 1 is carried out beforethe wafer 1 is transferred to the sub-arm mechanism 112 (Step S3). Thatis, a light-emitting section and a light-receiving sensor are arrangedat the periphery of the wafer 1, opposing each other. The Zθ drivemechanism 154 rotates the wafer 1, and the wafer 1 is stopped uponrotating through a particular angle when the notch 1 b (see FIG. 1) isdetected.

[0237] When the notch alignment of the wafer 1 is completed, the wafer 1is transferred to the sub-arm mechanism 112 (Step S4). The sub-armmechanism 112 transports the wafer 1 and holds it right above the maskmember 4 which has been set in the resist solution applying mechanism113.

[0238] (2) Actuation of the Nozzle Unit (Steps S6 to S9)

[0239] The nozzle unit 2 waits, set in the nozzle unit station 129 asshown in FIG. 4, until the wafer 1 is positioned in the resist solutionapplying mechanism 113 (Step S6).

[0240] At this time, the solution supply valve 140 and the solvent valve144 are closed and opened, respectively, as mentioned above. The solventtherefore continuously passes through the small discharge hole 130 amade in the nozzle 130, thus preventing the clogging and drying.

[0241] When preparation for the application of resist solution to thewafer 1 is completed, the nozzle unit 2 is actuated. More precisely, thesolvent valve 144 is closed, stopping the discharging of solvent (StepS7). The solution supply valve 140 is opened, supplying the resistsolution into the discharge hole 130 a (Step S8). As the resist solutionis supplied into the discharge hole 130 a, the solution supply valve 140is closed, and the nozzle 2 is moved from its waiting position to aposition in the solution applying mechanism 113 (where the nozzle 2oppose the point START shown in FIG. 1) (Step S9).

[0242] While the wafer 1 and the nozzle unit 2 are being loaded, thesolvent atmosphere is continuously controlled in the solution applyingmechanism 113. That is, the solvent in the solvent channel 122 of thesolution applying mechanism 113 is kept controlled in temperature andsurface level. The solvent atmosphere is controlled by an atmospherecontrolling section 161 provided in the central control section 147.

[0243] (3) Application of the Resist Solution (Step S10)

[0244] When the wafer 1 is positioned in the solution applying mechanism113, the central control section 147 moves the nozzle unit 2 and wafer1, relative to each other, in accordance with the solution applicationroute and relative speed set by a route-speed setting section 152 andalso with other conditions. The resist solution is thereby applied tothe wafer 1.

[0245] In the present embodiment, the nozzle unit 2 is driven back andforth in the X direction from the point START shown in FIG. 12, whilebeing intermittently moved at turning points in the Y direction at acertain pitch. The wafer 1 is thereby coated with the resist solution.

[0246] To move the nozzle unit 2 along the route shown in FIG. 12, it isnecessary to decelerate and accelerate the nozzle unit 2 at each turningpoint in the X direction. This may result in variation in the thicknessof resist solution film. In order to avoid such variation, the nozzleunit 2 is turned back above the mask member, that is, outside thecircuit-forming region 1 a of the wafer 1. Thus, the nozzle unit 2 ismoved at a constant speed over the entire the circuit-forming region 1a.

[0247] The film of the resist solution applied onto the wafer 1 isthereby adjusted in accordance with the diameter of the solution stream,the relative speed of the nozzle unit 2 and the spread of the resistsolution on the wafer 1. As a result, a solution film having a uniformthickness is formed on the circuit-forming region 1 a of the wafer 1.

[0248] In this embodiment, too, the evaporation of solvent is preventedby controlling the air flow during the application of resist solutionand the agitation of the film of resist solution applied is performed,in the same way as in the first embodiment.

[0249] (4) Unloading of the Wafer (Steps S11 to S13)

[0250] When the application of resist solution is completed, the sub-armmechanism 112 is moved back from the solution applying mechanism 113 andtransported to the reversing mechanism 111. Then, the wafer 1 is turnedupside down, in the direction reverse to the direction in which it hasbeen turned to be loaded. The wafer 1, thus turned, is transferred tothe main arm mechanism 110 (Steps S12 and S13).

[0251] The main arm mechanism 110 thereafter transports the wafer 1 tothe place where the next step (baking) is carried out, and loads thenext wafer 1 into the reversing mechanism 111 (Step S1 et. seq.)

[0252] (5) Holding of Nozzle at Nozzle Unit Station (Step S14)

[0253] Until the main arm mechanism 110 loads the next wafer 1, thenozzle unit 2 is held at the in the nozzle unit station 129 (Step S14).At this time, the solvent valve 144 is opened, thereby passing thesolvent through the discharge hole 130 a. This prevents the hole 130 afrom being clogged.

[0254] The structure described above can attain not only the advantagesof the first embodiment but also the following advantages.

[0255] First, interruption of the resist solution stream can be reliablyprevented, to form a thin film of solution that has a uniform thickness.

[0256] That is, when the resist solution in a manner of single-strokewriting, it necessary to apply the solution in as slender a stream aspossible and to prevent interruption of the solution stream in order toform a thing film of solution that has a uniform thickness. The solutionstream may probably be interrupted if the viscosity of the resistsolution changes during the application of the solution. Further, thereis high possibility that the resist solution nozzle is clogged, and itis also necessary to prevent such clogging.

[0257] In the present invention, the wafer 1 is turned upside down, andthe resist solution is discharged upwards from the nozzle unit 2,coating the wafer 1 with the solution. Thus, the solvent atmosphere inthe space right below the wafer 1 can be easily maintainedappropriately. The solution stream can therefore be always maintained ata constant viscosity, however slender the solution stream is. Thisprevents interruption of the stream of the resist solution.

[0258] That is, the solvent contained in the resist solution evaporatesand flows upwards. In the ordinary coating method, the solvent easilyevaporates because from the resist solution because the resist solutionis applied to the upper surface of a wafer. It is therefore requiredthat a special structure be employed to maintain the solvent atmospherewith high precision when the solution is applied in a manner ofsingle-stroke writing as in the present invention.

[0259] By contrast, in the present invention, a solution-applying spaceis provided at the lower surface of the wafer 1, whereby the wafer 1serves as a cover. Thus, an appropriate solvent atmosphere can bemaintained and can prevent interruption of the stream of resistsolution, without the necessity of employing a complex structure.

[0260] If the case of applying the resist solution in this manner, thespread of resist solution is more inhibited after the resist solutionhas been applied, than in the case where the resist solution is appliedto the upper surface of the wafer. Hence, the solvent is effectivelyprevented from evaporating from the resist solution applied to thewafer.

[0261] As a result, the change in the viscosity of resist solution,which occurs at about the start and end of applying the solution can bereduced to a minimum. This can contribute to the enhancement ofresolution.

[0262] Second, air can be easily expelled from the nozzle unit.

[0263] Namely, since the discharge hole 130 a of the nozzle 130 opensupwardly in the structure according to this invention, air can beautomatically expelled when the nozzle is replaced with another. Neithera specific step nor a special structure is required to expel air fromthe nozzle.

[0264] The second embodiment is not limited to the structure describedabove.

[0265] First, the mechanism for preventing the clogging in the dischargehole of the nozzle unit is not limited to the one shown in FIG. 3. Anyother structure may be utilized.

[0266] For example, a cover for covering the distal end of the nozzleunit may be provided, in addition to the nozzle unit station.

[0267] Second, the solution application route is not limited to the onethat is illustrated in FIG. 12. Rather, it may be spiral as in the firstembodiment or may be of any other type. In order to form a film ofresist solution that has a uniform thickness, the resist solution may beapplied twice, first in one direction and then in another.

[0268] Third, the solution used to form a film is resist solution in theapparatus of this embodiment, as in the first embodiment. Nonetheless,the solution is not limited to resist solution. Any other solution maybe applied, instead. Examples of other solutions are a solution forforming an interlayer insulating film, a solution for forming a highlyconductive film, a ferroelectric solution, sliver paste, and the like.Further, the substrate to be processed is not limited to a semiconductorwafer 1; instead, it may be an LCD substrate or an exposure mask.

[0269] Fourth, a mask member 4 is provided in the first embodiment.Nevertheless, this member need not be provided. If this is the case, itsuffices to provide a mechanism for discharging residual resistsolution, such as a cup, below the wafer 1, to receive the residualresist solution.

[0270] Moreover, the mask member may be of any one of the types shown inFIGS. 11A to 11D. If so, the apparatus can be made smaller.

[0271] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

1. A method of forming a film on a surface of a substrate, comprisingthe steps of: holding a substrate to be processed; and driving thesubstrate and a nozzle unit relative to each other, while continuouslyapplying film-forming solution, in the form of a slender stream, to thesurface of a substrate, thereby to form a film on the substrate.
 2. Amethod according to claim 1, further comprising a step of covering thesubstrate, except a film-forming region thereof, with a mask member. 3.A method according to claim 1, further comprising a step of vibratingthe substrate coated with the solution, thereby to render flat a surfaceof a solution film formed on the substrate.
 4. A method according toclaim 1, which further comprises a step of holding the substrate, withthe surface, on which a film is to be formed, turned downwards, and inwhich the substrate and a nozzle unit are driven relative to each other,while continuously applying film-forming solution, in the form of aslender stream, to a surface of a substrate, thereby to form a film onthe substrate.
 5. A method according to claim 4, further comprising astep of turning the substrate upside down to hold the substrate with thesurface turned downwards.
 6. A method according to claim 4, furthercomprising a step of holding the nozzle unit at a wait position, beforea film is formed on the substrate, in which solvent is passed throughthe discharge hole of the nozzle unit, thereby to prevent clogging inthe discharge hole.